L-Rhamnopyranosyl

Welan is produced by 2is Pilcaligenes species (ATCC-31555) by aerobic fermentation, and marketed under the trade name BIOZAN (Merck and Co., Inc.) early reports also referred to it as S-130 (229). The polymer is stmcturaUy similar to geUan, sharing the same backbone sequence. It has an additional side group of an a-L-rhamnopyranosyl or an a-L-maimopyranosyl (Man ) unit linked (1— 3) to a P-D-glucopyranosyl unit in the backbone of the polymer ... 

Poly-[(3,6-Di-0-methyl-P-D-glucopyranosyl)-(1->4)-(2,3-di-0-methyl-a-L-rhamnopyranosyl)-(1 ->2)-(3-0-methyl-a-L-rhamnopyranosyloxy)-(1-0->4 )-(3-phenylpropanoyl)-(1->NLys]-protein... 

Rhodinose Rutinose 2,3,6-T rideoxy-L- threo- hexose a-L-Rhamnopyranosyl-(1->6)-D-glucose... 

Sarmentose Sedoheptulose Sedoheptulosan Solatriose 2.6- Dideoxy-3-0-methyl-D-xy/o-hexose D-a/froHept-2-ulose 2.7- Anhydro P-D-a/fro-hept-2-ulopyranose a-L-Rhamnopyranosyl-(1 ->2)-[P-D-glucopyranosyl-(1->3)]-D-galactose... 

A (1 — SO-coupled compound between methyl (3/ )-3-[(3 / )-3 -hydroxy-decanoyloxy]decanoate and 2-0-a-L-rhamnopyranosyl-o -L-rhamnopyra-nose, a rhamnolipid from Pseudomonas aeruginosa, expected to have various biological activities, was prepared by double couplings using 3,4-di-0-benzyl-2-0-chloroacetyl-a-L-rhamnopyranosyl fluoride (by the BFj- OEtj method). 

D-Mannose is common, but L-mannose has only been found in a small group of extracellular polysaccharides of related structures, one of which is elaborated by Alcaligenes ATCC 31555. In these polysaccharides, it is a-linked and partially replaces an a-L-rhamnopyranosyl residue in the pentasaccharide repeating-unit. It seems possible that these sugar residues are scrambled, but the other possibility, that there are two populations of polysaccharides, has not yet been excluded. 

The pyruvic acid may also be linked to vicinal positions. When linked to 0-3 and 0-4 of a D-galactopyranosyl residue (40), the dioxolane ring becomes cw-fused. In the limited number of known examples, the absolute configuration at the acetalic carbon atom is (S), as in 40. There are some examples of tra -fused dioxolane rings, and these are more sensitive to hydrolysis with acid than the others. Thus, pyruvic acid is acetalically linked to 0-3 and 0-4 of an a-L-rhamnopyranosyl residue in the Klebsiella type 72 capsular polysaccharide, to 0-2 and 0-3 of an a-D-galactopyranosyl residue in the Streptococcus pneumoniae type 4 capsular polysaccharide, and to 0-2 and 0-3 of a S-D-glucopyranosyluronic acid residue in the Klebsiella K1 capsular polysaccharide. " In the extracellular polysaccharide from... 

The steroidal aglycon carries a neohesperidosyl group at one end and an a-L-rhamnopyranosyl group at the other. 

Nygaard, A. et al., Stracture determination of 6-hydroxycyanidin- and 6-hydroxydel-phinidin-3-(6"-o-a -L-rhamnopyranosyl-b -D-glucopyranosides) and other anthocyanins from Alstroemeria cultivars, Acta Chem. Scand., 51, 108, 1997. 

D-glucopyranoside congeners, (Z)-3-hexenyl 6-0-(3-D-xylopyranosyl-(3-D-glucopyranoside (74), (Z)-3-hexenyl 6-0-a-L-arabinopyranosyl-(3-D-glucopyra-noside (75) and (Z)-3-hexenyl 6-0-a-L-rhamnopyranosyl-(3-D-glucopyranoside... 

The coupling reaction of 78 with 2 equivalents of the reported 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl bromide in the presence of AgOTf and TMU in CH2CI2 gave the coupled product (81) in 56% yield. Finally, treatment of 81 with NaOMe in MeOH-THF provided the synthetic (3Z)-hexenyl 6-O-a-L-rhamnopyranosyl-p-D-gluco-pyranoside (76) in 96% yield. 

Pectins are heteropolysaccharides with axial-axial a(1, 4)-D galactopyranosyluronic acid units condensed in the Ci conformation and interrupted by a-(1,2)-L rhamnopyranosyl residues. The structure is based on blocks of galacturonan partly esterified (the smooth zones) and blocks of highly ramified rhamnogalacturonan regions (hairy zones). The exact structure depends on the sources but also on the methods used to isolate the pectins [1,5]. Few data are given in Table 1. 

Mutter M, Colquhoun IJ, Schols HA, Beldman G, Voragen AGJ (1996) Rhamnogalacturonase B from Aspergillus aculeatus is a rhamnogalacturonan a-L-rhamnopyranosyl-(l->4)-a-D-galactopyranosyluronide lyase. Plant Physiol 110 73-77... 

The detected rhamnose residues were typical for the backbone of pectin. Some of the (l- 2)-linked a-L-rhamnopyranosyl residues were branched, having side chains attached to 0-4 and to 0-3. Additionally terminal and double branched rhamnose residues were found in small amounts. Fiiudly typical fucose and xylose residues were detected in all the analysed fractions. 

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